3GPP (3rd Generation Partnership Project) is a project for discussing/creating specifications of a mobile communication system based on a network developed from W-CDMA (Wideband-Code Division Multiple Access) and GSM (Global System for Mobile Communications). The 3GPP has standardized the W-CDMA mode as a third-generation cellular mobile communication mode and the services are sequentially started. HSDPA (High-Speed Downlink Packet Access) with higher communication speed has also been standardized and the service is started. The 3GPP is currently discussing about a mobile communication system (hereinafter referred to as “LTE-A (Long Term Evolution-Advanced)” or “Advanced-EUTRA”) that utilizes the development of the third generation radio access technology (hereinafter referred to as “LTE (Long Term Evolution)” or “EUTRA (Evolved Universal Terrestrial Radio Access)”) and a wider frequency band to realize faster data transmission/reception.
The OFDMA (Orthogonal Frequency Division Multiple Access) system and the SC-FDMA (Single Carrier-Frequency Division Multiple Access) system which perform user-multiplexing using subcarriers that are orthogonal to each other are discussed as communication systems in LTE. The OFDMA system that is a multi-carrier communication system is proposed for downlink, and the SC-FDMA mode that is a single-carrier communication system is proposed for uplink.
On the other hand, for communication systems in LTE-A, it is discussed to introduce the OFDMA system for downlink and the Clustered-SC-FDMA (Clustered-Single Carrier-Frequency Division Multiple Access, also referred to as DFT-s-OFDM with Spectrum Division Control) system, in addition to the SC-FDMA system, for uplink. The SC-FDMA system and the Clustered-SC-FDMA system proposed as uplink communication systems in LTE and LTE-A are characterized in that PAPR (Peak to Average Power Ratio) at the time of transmission of data (information) can be suppressed to a lower level.
While a typical mobile communication system uses a continuous frequency band, it is discussed for LTE-A to use a plurality of continuous/discontinuous frequency bands (hereinafter, referred to as “carrier elements, carrier components (CC)” or “element carriers, component carriers (CC)”) in a multiple manner to implement operation as one frequency band (broad frequency band) (frequency band aggregation, also referred to as spectrum aggregation, carrier aggregation, and frequency aggregation). It is also proposed to give different frequency bandwidths to a frequency band used for downlink communication and a frequency band used for uplink communication so that a base station apparatus and a mobile station apparatus more flexibly use a wider frequency band to perform communication (asymmetric frequency band aggregation: asymmetric carrier aggregation) (Nonpatent Document 1).
FIG. 17 is a diagram for explaining frequency band aggregation in a conventional technique. Giving the same bandwidth to a frequency band used for the downlink (DL) communication and a frequency band used for the uplink (UL) communication as depicted in FIG. 17 is also referred to as symmetric frequency band aggregation (symmetric carrier aggregation). As depicted in FIG. 17, a base station apparatus and a mobile station apparatus use the plurality of carrier components that are continuous/discontinuous frequency bands in a multiple manner, thereby performing communication in a wider frequency band constituted of the plurality of carrier components. In FIG. 17, by way of example, it is depicted that a frequency band used for the downlink communication with a bandwidth of 100 MHz (hereinafter also referred to as DL system band or DL system bandwidth) is constituted of five carrier components (DCC1: Downlink Component Carrier 1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz. By way of example, it is also depicted that a frequency band used for the uplink communication with a bandwidth of 100 MHz (hereinafter also referred to as UL system band or UL system bandwidth) is constituted of five carrier components (UCC1: Uplink Component Carrier 1, UCC2, UCC3, UCC4, and UCC5) each having a bandwidth of 20 MHz.
In FIG. 17, downlink channels such as a physical downlink control channel (hereinafter, PDCCH) and a physical downlink shared channel (hereinafter, PDSCH) mapped on each of the downlink carrier components. The base station apparatus uses the PDCCH to transmit to the mobile station apparatus control information (such as resource allocation information, MCS (Modulation and Coding Scheme) information, and HARQ (Hybrid Automatic Repeat Request) process information) for transmitting a downlink transport block transmitted by using the PDSCH, and uses PDSCH to transmit the downlink transport block to the mobile station apparatus. Therefore, in FIG. 17, the base station apparatus can transmit up to five downlink transport blocks to the mobile station apparatus in the same sub-frame.
Also, uplink channels such as a physical uplink control channel (hereinafter, PUCCH) and a physical uplink shared channel (hereinafter, PUSCH) mapped on each of the uplink carrier components. The mobile station apparatus uses PUCCH and/or PUSCH to transmit to the base station apparatus control information (control signals) such as HARQ control information for the physical downlink control channel and/or the downlink transport blocks, channel state information, and scheduling requests. The HARQ control information is information indicative of ACK/NACK (Positive Acknowledgement/Negative Acknowledgement, ACK signal or NACK signal) and/or information indicative of DTX (Discontinuous Transmission) for the physical downlink control channel and/or the downlink transport blocks. The information indicative DTX is information indicating that the mobile station apparatus cannot detect the PDCCH from the base station apparatus. In FIG. 17, any of downlink/uplink channels such as the PDCCH, the PDSCH, the PUCCH, and the PUSCH may not be mapped on some downlink/uplink carrier components.
Similarly, FIG. 18 is a diagram for explaining asymmetric frequency band aggregation (asymmetric carrier aggregation) in a conventional technique. As depicted in FIG. 18, the base station apparatus and the mobile station apparatus give different bandwidths to a frequency band used for the downlink communication and a frequency band used for the uplink communication, and use the carrier components constitute these frequency bands in a multiple manner, thereby performing communication in a wider frequency band. In FIG. 18, by way of example, it is depicted that a frequency band used for the downlink communication with a bandwidth of 100 MHz is constituted of five carrier components (DCC1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz, and that a frequency band used for the uplink communication with a bandwidth of 40 MHz is constituted of two carrier components (UCC1 and DCC2) each having a bandwidth of 20 MHz. In FIG. 18, the downlink/uplink channels are mapped on each of the downlink/uplink carrier components, and the base station apparatus uses the plurality of PDSCHs allocated by the plurality of PDCCHs to transmit the plurality of downlink transport blocks in the same sub-frame to the mobile station apparatus. The mobile station apparatus uses the PUCCH and/or the PUSCH to transmit the control information (the control signals) such as the HARQ control information, the channel state information, and the scheduling requests, to the base station apparatus.